Purdue's On the Farm program submitted 99 crop samples for lab testing in 2025-up from 62 in 2024. Of those, 83 samples were from corn, and a striking 65 of those showed confirmed insect or disease damage. That's a significant leap from just 18 confirmed corn cases the previous year.

By contrast, soybean submissions remained flat, with 16 samples in 2024 and 16 again in 2025. Disease confirmations for soybeans stayed at eight samples, indicating little to no increase in pest pressure.

Southern Rust Outpaces Tar Spot

The timing and weather patterns in 2025 created an environment ripe for disease outbreaks. While tar spot continued to be a major concern, southern rust appeared more aggressively, outpacing tar spot 2-to-1 in confirmed cases by late August.

"This was a tough year for corn," said experts from Purdue. "Warm, moist conditions in late summer triggered rapid disease development across many counties."

By late July, lab results had already flagged diplodia leaf streak in corn and anthracnose in both corn and soybeans. While these diseases didn't dominate headlines like southern rust, they remain critical in assessing grain quality and harvestability.

"Diplodia has the potential to degrade grain post-harvest, especially in wet storage," notes one Purdue agronomist. "Anthracnose, meanwhile, can affect standability and ease of harvest in both crops."

Impact on Yields and Storage

Although USDA's final Indiana yield data won't be available until next year, the damage reports suggest a hit to corn quality and possibly overall yields in affected areas. With harvest nearing completion, attention turns to on-farm grain storage.

Both land-grant institutions and private consultants are preparing storage advisories, but much depends on farmers' observations during harvest. Early intervention and accurate diagnostics are expected to be key in minimizing post-harvest losses.

Looking Ahead to 2026

The sharp increase in disease confirmations has experts urging farmers to review fungicide programs, consider hybrid resistance traits, and closely monitor environmental conditions throughout the growing season.

"Every crop year brings its own set of challenges," Purdue's team emphasized. "In 2025, we were lucky it didn't get worse, given the disease-favorable weather. This should be a wake-up call to adapt ahead of 2026."